Types Of Broaching Machine – Classification Of Broaching Machine

Broaching machines act as facilitators between broach and workpiece. Broaching machines provide fixture to the broach, central (precise) to all motions of broach and workpiece and required relative motions between broach and workpiece. These machines are very simple as they only have to move the broach tool in a linear motion at a predetermined speed and provide a means for handling the broach automatically.

Read more : Introduction To Broaching Operation | Advantages and Disadvantages

types of broaching process
types of broaching process

Types Of Broaching Machine

These machines can be categorized on the basis of different criterion as described below.

Working principle can be criteria of classification of broaching machine as described below :
(a) Hydraulic broaching machine
(b) Mechanical broaching machine
(c) Electro-mechanical broaching machine
(d) Computer controlled broaching machine

Construction of a broaching machine can also be another criteria of classification like :
(a) Vertical broaching machine
(b) Horizontal broaching machine
(c) Rotary broaching machine

Application of a broaching machine can also be criteria of classification of a broaching machine :
(a) internal broaching machine
(b) external broaching machine

Hydraulic Broaching Machine
Hydraulic broaching works with the help of high pressure fluid called hydraulic fluid. The fluid pressure and its precise variation provides motive power to various components of the machine. This fluid pressure is distributed and controlled directly and automatically by control values and hoses and tubes. Advantage of hydraulic system is its precise control and capability to transfer huge power through small tubes and flexible hoses.

Mechanical Broaching Machine
In mechanical machine power is generated electrically at its motor and then it is transferred to its various components like broach holder, worktable feed mechanism, etc. through belt, gears, etc.

Electromechanical Broaching Machine
Electromechanical broaching machine is a move towards automation. In this machine all the centrals of process parameters are controlled with the help of electronic control. However, generation of power and transmission of power from the place of generation to various components is like hydraulic machine or mechanical broaching machine. There are possibilities of development of computer controlled broaching machine. There are possibilities of entering program which can execute more than one operation in proper sequence without any time gap. Process capability and accuracy of electromechanical or computer controlled broaching machines are very good as compared to other machines.

On the other basis of construction different type of broaching machines are described below.

Vertical Broaching Machine
In case of vertical broaching machine movement of broach is in vertical direction. These machines may have the stroke length more than 1.5 meter. Vertical broaching machines can be designed for push broaching, pull down broaching, pull-up broaching or surface broaching. Normally surface broaching is done by vertical broaching machine.

Horizontal Broaching Machine
In case of horizontal broaching machine, movement of broach is in horizontal direction. Thee machines are normally designed for pull broaching, surface broaching, continuous broaching and rotary broaching. These machines are not so popular as the vertical broaching machines.

Rotary Broaching Machines
Generally a rotary broaching machine requires two important tooling components a tool holds and a broach. The broach is mounted in the tool holder that facilitates it to freely rotate. The tool holder is specially designed so that it can hold the tool keeping its axis of rotation slightly inclined (1 to 2o) to the axis of rotation of the workpiece. This small misalignment helps the broach in cutting. The cutting action is named as “wobbling” and the broach mounted in this way is called “wobbling broach”. It is not necessary to use broaching machine in case of rotary broaching. This can be done with the help of lathe machine. The required rotary motion to the broach can be given by the cluch of the lathe.

On the basis of application the broaching machines are classified as described below.
Internal Broaching Machine
Internal broaching refers to broaching of inner surface of a round hole, slot or groove. Internal broaching machines are not different but it can be carried out on any of the above type of machines. Internal broaching is also used for making internal gears. Smoothening of gun barrel bore is also done by internal broaching. In case of internal broaching the workpiece is clamped into a special holding fixture called work holder which is inbuilt in the broaching machine. Elevator is another part (component) of the broaching machine that moves the broach above the work holder, then lower the broach through the workpiece. Once through, the broaching machine’s puller essentially a hook, grabs the pilot of the broach. The elevator then releases the top of the pilot and the puller pulls the broach through the workpiece completely. The workpiece is the removed from the machine and broach through the workpiece completely. The workpiece is then removed from the machine and the broach is raised back up to re-engage with the elevator.

External Broaching Machine
These are also called surface broaching machines. These machines are used to process external surfaces of workpiece. External broaching machines are also used for contour broaching. Contour broaching involves preparation of concave or convex surfaces or any other shape with extremely close tolerances.

Continuous Broaching Machine
Continuous broaching machine is a different type of classification. These machines can be horizontal or vertical type. The concept of continuous broaching machine is concerned with continuity. This continuity of operation can be maintained by keeping the broach stationary and moving workpiece through the tool (broach) to perform cutting. In case of horizontal continuous broaching machines two sprockets, one on each side of the machine, are maintained. On the sprockets, there is continuous travel of an endless chain having a series of fixtures mounted on it. The broaches are rigidly hold on the machine in horizontal position over the chain. Workpieces are loaded on the fixtures on one side of the machine and unloaded on its over sides shown in Figure

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